Store and Recall Object Transformation
I too would like a Pose Library for objects that aren't bones, but that doesn't mean you can't use bones and the Pose Library to do this.

First put a single bone armature in your object. 
Press Shift + A, Add > Armature > Single Bone. Move the bone inside your object. Select the object and then Shift select the bone. Press Ctrl + C, and choose Armature Deform > With Automatic Weights.
(you might want to check the box "In Front", so you can see the bone even when it is inside the object. Located here: Properties > Object Data Properties > Viewport Display)


You can't add a pose in object mode, so select the bone and go to Pose Mode in the 3D Viewport. In the Properties window go to Object Data Properties > Pose Library. Then add a pose by clicking the little plus icon. (If you already have a pose, choose: "Replace existing..." and select your pose.)


Now rotate the bone and the child object rotates with it. To reset the rotation to the state when you added the pose, simply click on the little magnifier icon, while your pose is selected in the Pose Library.